1. Field of the Invention
Embodiments of the present invention generally relate to substrate plasma processing apparatus and methods adapted to deposit a film on a surface of a substrate.
2. Description of the Related Art
Physical vapor deposition (PVD) using a magnetron is one of the principal methods of depositing metal onto a semiconductor to form electrical connections and other structures in an integrated circuit device. During a PVD process a target is electrically biased so that ions generated in a process region can bombard the target surface with sufficient energy to dislodge atoms from the target. Such a process is commonly called sputtering. The sputtered atoms travel generally toward the wafer and are deposited on the wafer. Alternatively, the atoms react with a gas in the plasma, for example, nitrogen, to reactively deposit a compound on the wafer. Reactive sputtering is often used to form thin barrier and nucleation layers of titanium nitride or tantalum nitride on the substrate.
Direct current (DC) magnetron sputtering is the most usually practiced commercial form of sputtering. The metallic target is biased to a negative DC bias in the range of about −100 to −600 VDC to attract positive ions of the working gas (e.g., argon) toward the target to sputter the metal atoms. Usually, the sides of the sputter chamber are covered with a shield to protect the chamber walls from sputter deposition. The shield is typically electrically grounded and thus provides an anode in opposition to the target cathode to capacitively couple the DC target power to the plasma generated in the sputter chamber.
A magnetron having at least a pair of opposed magnetic poles is typically disposed near the back of the target to generate a magnetic field close to and parallel to the front face of the target. The induced magnetic field from the pair of opposing magnets trap electrons and extend the electron lifetime before they are lost to an anodic surface or recombine with gas atoms in the plasma. Due to the extended lifetime, and the need to maintain charge neutrality in the plasma, additional argon ions are attracted into the region adjacent to the magnetron to form there a high-density plasma. Thereby, the sputtering rate is increased.
However, conventional sputtering presents challenges in the formation of advanced integrated circuits on large area substrates such as flat panel display substrates. Typically, for thin film transistor (TFT) display applications, the substrate is a glass substrate with a surface area greater than about 2000 cm2. Some TFT manufacturers have found that performing PVD processes on substrates greater than about 19,500 cm2 (e.g., 1300 mm×1500 mm) in size tend to have a greater degree of non-uniformity than sizes smaller than 19,500 cm2.
Therefore, there is a need for a method and apparatus that can improve the uniformity of the PVD deposited film.